fix: Lcov file not found (#97)

* fix: Lcov file not found

see github actions fail -> https://github.com/hexojs/hexo-renderer-stylus/runs/6463877524?check_suite_focus=true

* Update package.json

package.json

@@ -6,7 +6,7 @@
   "scripts": {
     "eslint": "eslint .",
     "test": "mocha test/index.js",
-    "test-cov": "nyc npm run test"
+    "test-cov": "nyc --reporter=lcov --reporter=text npm run test"
   },
   "directories": {
     "lib": "./lib"